Alternators installed in motor vehicles are driven directly by the vehicle engine. The driving is generally realized with belt drives. High requirements in terms of force transmission are placed on belt drives, whether they are V-belts or ribbed V-belts. The belt material must have extensive bending strength. Moreover, the linear extensional strain over the course of ageing must be as minimal as possible in order to prevent slip—combined with excessive heating-up and wear—of the belt.